Cooling with microwave excited micro-plasma and ions

ABSTRACT

One embodiment of the present invention uses an actuator, which is actuated by electromagnetic microwave. The actuator is used to generate the micro-plasma and ions. The configurations of actuators may be microstrip lines structure, stripline structure, piping structure, multiplayer traces and electrodes structure, waveguide structure, and cavity structure. The generated micro-plasma and ions will induce a local turbulent gas flow and the flow is to carry the heat away from the surfaces of the heat sink fins. The actuators may be coupled to heat sink fins, heat transferring pipes, cooling fans, and heat sources in varied configurations.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to electronic equipment, andmore particularly, to apparatus and methods for cooling electronicdevices using microwave excited micro-plasma and ions.

2. Description of the Related Art

Electronic devices may generate significant heat during operation. Hightemperatures may reduce the lifespan of these devices, and, therefore,the generated heat may need to be dispersed to keep the operatingtemperature of the electronic devices within acceptable limits.

One commonly used cooling device is heat sink. Heat sinks may be coupledto electronic devices to absorb heat through the heat sink base anddisperse the heat through their fins. Conventional methods to dispersethe heat through the heat sink fins are natural convection and forcedconvection. Natural convection is to disperse the heat away from thesurfaces of heat sink fins without the aid of external forced fluidpumping through heat sink fins. On the other hand, the forced convectioncooling is to pump the fluid to flow through heat sink fins, such as thefans to blow the air through the heat sink fins, and therefore enhancethe heat transfer between fins and outside ambient.

With the increasing power density of electronic devices, the pitch orthe distance between heat sink fins is becoming smaller, which meansmore surface area may be used to transport the heat away. However, whenthe pitch becomes very small, the pressure drop between inlet and outletof the heat sink fins may become very high, which may results thedifficulties to pump the fluid flowing through fins, and as a result,more powerful fans, which consume higher electricity may be needed forthe cooling. The invention utilizes microwave excited micro-plasma andions to induce the gas flow to conduct the convective heat transferalong the heat sink fins and therefore will resolve these issues.

Another consideration of the electronic device cooling is that, due tosize concern, the internal space allowed to put cooling fans and othercooling components, may be limited or not permitted. The inventionutilizes the microwave excited micro-plasma and ions gas flow togenerate the forced convective heat transfer. Therefore the design isable to improve the heat transfer efficiency and to minimize therequired space because microwave excited micro-plasma and ions can bevery small.

Another aspect of using the invention is to lower the required power ofthe system fans of electronic devices. The micro-plasma and ions drivengas flow excited by the microwave couple with the heat sink fins willinduce the local turbulence gas flow near heat sink surfaces. The localturbulence near the heat sink surface will enhance the heat dissipationso a better cooling is achieved. Therefore the system fan doesn't needto be very powerful and the electricity energy is saved.

Plasma-driven gas flow has been used either to cool articles or tocontrol and modify the fluid dynamics boundary layer on the wingssurfaces of the aerodynamic vehicles. For example, U.S. Pat. No.3,938,345 used the phenomenon of corona discharge, which is one type ofplasma, to do the local cooling of an article. U.S. Pat. No. 4,210,847designed an apparatus for generating an air jet for cooling application.U.S. Pat. No. 5,554,344 had a gas ionization device to do the cooling ofzone producing chamber. U.S. Pat. No. 6,796,532 B2 used a plasmadischarge to manipulate the boundary layer and the angular locations ofits separation points in cross flow planes to control the symmetry orasymmetry of the vortex pattern.

However, none of the above patents are coupled to the heat sink, whichis a fundamental apparatus for cooling electronic devices. Hence, whatare needed are a method and an apparatus, to couple with heat sink finsto cool down electronic devices efficiently.

SUMMARY OF THE INVENTION

One embodiment of the present invention provides a microwave excitedmicro-plasma and ions couple to heat sink fins to induce the gas flowalong the heat sink fins. The induced gas flow will remove the heat awayfrom heat sink fin surface and therefore the heat source is cool down.

In one embodiment, the cooling system includes heat sink fins assemblyand array of the microwave excited micro-plasma and ions devices. Theheat sink fin assembly may be composed by a plurality of straight heatsink fins, a plurality of heat sink pins, or other shapes of finstructure. The micro-plasma and ions devices may be composed withdifferent configurations, such as micro-strips, microwave wave guides,and microwave cavities. The micro-plasma and ions may be excited andgenerated at different locations inside the heat sink fin assembly.

In one embodiment, the micro-plasma and ions may be excited andgenerated with microwave cavities, which have slots, holes, or trench onthe surface of the microwave wave guide structure. In a furtherembodiment, the generated micro-plasma and ions will couple and interactwith heat sink fins assembly to do the cooling.

In one embodiment, the micro-plasma and ions actuators may be configuredby one or several micro-strips. In another embodiment, theconfigurations of the micro-strips may be varied to gain the maximumelectrical field at specific regions to induce micro-plasma and ions.

In one embodiment, the micro-plasma and ions actuators may be composedof microwave wave guides, which have different configurations such aspipe shape, micro-strip shape, rectangular shape, or other shapes. Thedielectric layers may couple with microwave wave guides.

In one embodiment, the applied microwave sources to excite and generatethe micro-plasma and ions flow may have varied waveforms, frequencies,amplitude, phase shifts, and may be transient.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention may be obtained when thefollowing detailed description is considered in conjunction with thefollowing drawings, in which:

FIG. 1 illustrates a micro-plasma and ions generating device;

FIG. 2 illustrates a micro-plasma and ions generating device;

FIG. 3 illustrates an array of micro-plasma and ions devices;

FIG. 4 illustrates an array of micro-plasma and ions devices couple to aheat sink fins assembly;

FIG. 5 illustrates an array of micro-plasma and ions devices couple to aheat sink fins assembly;

FIG. 6 illustrates an array of micro-plasma and ions devices couple to aheat sink fins assembly;

FIG. 7 illustrates a micro-plasma and ions device couple to a heat sinkfins assembly;

FIG. 8 illustrates the micro-plasma and ions devices couple to a heatsink fins assembly in varied configurations;

FIG. 9 illustrates the micro-plasma and ions devices made ofmicro-strips;

FIG. 10 illustrates the microwave waveguides coupled with microwavecavities are used to excite and generate micro-plasma and ions;

FIG. 11 illustrates the microwave waveguides and microwave cavities areused to excite and generate micro-plasma and ions;

FIG. 12 illustrates the micro-plasma and ions coupled with heat sinkfins;

FIG. 13 illustrates the micro-plasma and ions actuator is used to cooldown the heat sources inside an electronic device.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that the drawings and detaileddescription thereto are not intended to limit the invention to theparticular form disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the present invention as defined by the appendedclaims. Furthermore, note that the word “may” is used throughout thisapplication in a permissive sense (i.e., having the potential to, beingable to), not a mandatory sense (i.e., must). The term “include”, andderivations thereof, mean “including, but not limited to”. The term“coupled” means “directly or indirectly connected”.

DETAILED DESCRIPTION OF THE INVENTION

The invention generally relates to apparatus for cooling electronicdevices or packages, such as microprocessor and ASIC. Such systems andmethods may be used in a variety of applications. A non-exhaustive listof such applications includes the cooling of: a microprocessor chip, agraphics processor chip, an ASIC chip, a video processor chip, a DSPchip, a memory chip, a hard disk drive, a graphic card, a portabletesting electronics, a personal computer system.

Take laptop computer for example, conventional fans use a lot of spaceand energy. For this reason, the microwave excited micro-plasma and ionscooling represent a way to increase their cooling capacity and make themmore reliable and far quieter. Therefore the higher-performance chipsthat generate too much heat for current laptops can be used.

As used herein “plasma” is an ionized gas, a gas into which sufficientenergy is provided to free electrons from atoms or molecules and toallow both species, ions and electrons, to coexist. Plasma is evencommon here on earth. A plasma is a gas that has been energized to thepoint that some of the electrons break free from, but travel with, theirnucleus. Gases can become plasmas in several ways, but all includepumping the gas with energy. A spark in a gas will create a plasma. Ahot gas passing through a big spark will turn the gas stream into aplasma that can be useful. Plasma torches like that are used in industryto cut metals.

As used herein “dielectric” is a substance that is a poor conductor ofelectricity, but an efficient supporter of electrostatic fields. Inpractice, most dielectric materials are solid. An important property ofa dielectric is its ability to support an electrostatic field whiledissipating minimal energy in the form of heat. The lower the dielectricloss (the proportion of energy lost as heat), the more effective is adielectric material. Another consideration is the dielectric constant,the extent to which a substance concentrates the electrostatic lines offlux. Substances with a low dielectric constant include a perfectvacuum, dry air, and most pure, dry gases such as helium and nitrogen.Materials with moderate dielectric constants include ceramics, distilledwater, paper, mica, polyethylene, and glass. Metal oxides, in general,have high dielectric constants.

FIG. 1 illustrates a configuration of a micro-plasma and ions generatingdevice. The figure shows a microwave 101 is traveling along the axialdirection and the wave is between inner cylinder 102 and outer cylinder103. The dielectric material 102 is between two cylinders. Thedielectric material can be air or other materials. The plasma, as shownin the black color region 104 in the figure, may be excited andgenerated by the electromagnetic microwave and the plasma may flow outof the nozzle, which is located at the end of outer cylinder. Similarly,FIG. 2 illustrates another configuration. These configurations act asmicro-plasma and ions generators.

Similar to FIGS. 1 and 2, the plasma may be excited and generated byelectromagnetic microwave using micro-strip structure as shown in FIG.3. The micro-strips 105 are on one side of the dielectric material 102and the ground 106 is on the other side. The top micro-strips and bottomground may have extension on the side wall of the dielectric material asshown in the FIG. 3. The gap between top micro-strips 105 and the ground106 extension may be small in order to have high electrical fielddistribution when an electromagnetic microwave travels to there. In oneembodiment, the micro-plasma and ions actuators may be configured to bean array which has many channels. In another embodiment, the micro-stripmay have impedance matching stub, which is not shown here in the figure,to minimize the microwave reflection from the edge of the board.Furthermore, varied micro-strips patterns and different geometries ofthe micro-strip edge and ground edge may be used.

FIG. 4 illustrates an array of the circular-pipe shape micro-plasma andions actuators are assembled on one side of the heat sink fins assembly201. The generated micro-plasma and ions will induce local turbulentflow. This turbulent flow may couple with a fan, to enhance the heatremoval from the heat sink surface. In one embodiment, besides thecircular shape, the micro-plasma and ions actuators may have differentconfigurations, such as rectangular shape.

FIG. 5 illustrates an array of micro-strip actuators is coupled with theheat sink base 200 and heat sink fins 201 assembly. The micro-plasma andions generated by micro-strip make the design scaleable and themicro-plasma and ions can easily couple to heat sink fins 201 as shownin the figure. The micro-strips 105 may be deposited on one side of thedielectric 102 board and the other side may be electrically grounded106.

FIG. 6 illustrates another configuration of the micro-strips 105 coupledwith heat sink fins 201 and heat sink base 200. One single micro-strip105 may couple to a single heat sink fin 201 as shown in the FIG. 6. Inone embodiment, one micro-strip 105 may couple to several heat sink fins201 as shown in FIG. 7. In another embodiment, the bulk heat sink finsor the micro-channels heat sink fins may be used.

Not limited by the configurations of the FIG. 4 to FIG. 7, themicro-plasma and ions actuators may be coupled with heat sink fins 201assembly in varied directions and patterns. FIG. 8 illustrates the sideand top views of the micro-plasma and ions actuators coupled with heatsink fins 201 assembly and heat sink base 200. The black lines shown arethe micro-plasma and ions actuators. In one embodiment, the micro-plasmaand ions actuators may be manufactured with flexible materials so theycan be bended to fit with specific space and shape requirements, and maybe manufactured in a similar way as PCB manufacturing process. Inanother embodiment, the heat sink fins may be straight as shown in FIG.8 a to FIG. 8 d, and the heat sink fins may be configured with finstructure as shown in FIG. 8 e. Other geometries and shapes of heat sinkfins may be used to couple with micro-plasma and ions actuators and thevariation should be considered within the scope of the embodiment here.

FIG. 9 illustrates some configurations of the micro-strips used toexcite and to generate the micro-plasma and ions. FIGS. 9 a and 9 b showthe micro-strips 105 are on one side of the dielectric material 102 andthe ground metal 106 is on the other side. There is a small gap betweentop and bottom conductors on the side wall of the dielectric material102. The electromagnetic microwave is traveling inside the dielectricmaterial toward the gap region. The high electrical field, which isfavorable, will occur at the gap region to ionize the air and thereforethe plasma flow is induced. In one embodiment, the configuration of themicro-strips may be varied and the edge patterns may be varied as well.All the variation should be considered within the scope of theinvention. FIG. 9 c illustrates one configuration of the micro-strip 105and ground 106 coupled with dielectric material 102. In anotherembodiment, the embedded conductive traces and electrodes may be used asshown in FIG. 9 d. When electromagnetic interference is concerned, theembedded conductive traces and electrodes may be preferable because itcan help shield the electromagnetic wave. In a further embodiment,multi-layers conductive traces and electrodes structures may be used toprovide multi-channel capability and FIG. 9 e shows one example of theconfiguration. The electromagnetic microwaves exiting out the openingswill ionize the gas at the opening region and induce the turbulent flow.FIG. 9 e shows the openings are at in-plane direction. In oneembodiment, the openings are not limited to only in-plane direction, butmay be also at out-of-plane direction as shown in FIG. 9 f.

At very high electromagnetic frequencies, the losses due to radiationcan be eliminated and the resistive losses can be minimized, by usingclosed resonant cavities. A cavity resonator stores both magnetic andelectric fields, the energy oscillating between the two, losing energyonly to the conducting walls if a perfect dielectric fills the space.The resonant frequency of the cavity is determined by the shape of thecavity and the mode, or allowable field distribution, of theelectromagnetic energy that the cavity contains. In one embodiment, themicro-plasma and ions may be excited and generated by microwave cavitiesand varied forms of coupling of the electromagnetic microwave may beutilized. FIG. 10 illustrates one example of the TE10 wave-guide 301magnetically 303 coupled to a cylindrical resonator 302. The top view ofthe system is shown in FIG. 10 a and the side view is shown in FIG. 10b. In this case some of the magnetic field within the cavity leaksthrough an iris 305 cut into the sides of the wave-guide 301 and theresonator walls, thereby exciting waves in the guide, the larger theiris size, the stronger the degree of coupling. The locations ofopenings 306 to excite the micro-plasma and ions may be either on awave-guide structure or on a cavity resonator structure, as long as theelectrical field 304 at the locations is high enough to ionize the gas.In practical application, the locations where the maximum electricalfield 304 occurs are to be carefully designed. In one embodiment, theshape and the geometry of the microwave wave-guide and cavity structuresmay be varied. In a further embodiment, varied forms of electromagneticcouplings may be used to excite the micro-plasma and ions, then toinduce the turbulent flow. All the variations should be consideredwithin the scope of the invention here.

FIG. 11 illustrates the slots, holes, and trenches may be made on thewall of wave-guide 307 structure to provide the excitation of themicro-plasma and ions. Different configurations of the wave-guidestructure and varied geometries of the holes, slot, and trenches may beused. In another embodiment, different configurations of the microwavecavities 308 may be used to excite the micro-plasma and ions. Thelocation and size and geometry of the opening 309 where maximumelectrical field occur may be computationally calculated andexperimentally determined.

FIG. 12 illustrates the coupling between micro-plasma and ions 401 andheat sink fins 402. In one embodiment, the heat sink fins 402 may havedifferent configurations, such as, straight micro-channel heat sinkfins, cylindrical needle-shape pins, and the heat sink fins may havepatterns to couple with micro-plasma and ions 401. As mentioned earlier,the micro-plasma and ions 401 may be excited at the locations where thehigh electrical field occurs. The coupling of the heat sink fins 402with microwave may enhance the micro-plasma and ions gas flow and inducethe local turbulence flow in the fluid. In another embodiment, themicro-plasma and ions 401 may be excited and generated withelectromagnetic microwave from micro-strips, microwave cavities, andmicrowave thrusters structures.

FIG. 13 illustrates one example of the micro-plasma and ions coolingdevice 408 used to cool down the heat sources 405 inside an electronicdevice 400. The heat source 405, such as IC, may couple to micro-channelheat sink fins 407 through a heat transferring pipe 406, such as heatpipe. In this way, the heat will be dissipated out to a larger area. Themicro-plasma and ions cooling device 408 may couple to the micro-channelheat sink fins 407. The induced plasma gas flow will therefore cool downthe micro-channels heat sink fins 407. In one embodiment, themicro-plasma and ions may couple to a heat sink fan 411.

The micro-plasma and ions cooling actuator 408 may be made of wave guidestructure, microwave cavity structure, micro-strip structure, andembedded conductive traces and electrodes. The cooling actuator 408 maycouple to heat sink fins at the inlet, at the outlet, at the top, at thebottom, or in the middle of the heat sink fins 407. In one embodiment,all components may couple to a board 410, such as printed circuit board,so the entire device can be made very small. In another embodiment, theactuators may be made in a bulk scale, a micron meter scale, and a nanometer scale. Furthermore, the actuators may be directly manufactured ona silicon chip structure and the actuators may be manufactured withmicro-electro-mechanical wafer processing techniques;

1. A method and apparatus for cooling electronic devices, comprising: amicrowave excited micro-plasma and ions actuator coupled with coolingheat sink fins assembly to cool down heat sources;
 2. The apparatus ofclaim 1, wherein the actuator involves using an inner cylinder and anouter cylinder, a micro-strip structure, a stripline structure, embeddedconductive traces and electrodes, a wave-guide structure, and a cavitystructure for the electromagnetic microwave to pass through to ionizethe gas;
 3. The apparatus of claim 1, wherein the actuators arepopulated in an array to couple with heat sink fins assembly;
 4. Theapparatus of claim 1, wherein the actuators are coupled to a heat sinkfins assembly at the inlet, at the outlet, at the top, at the bottom,and in the middle of the heat sink fins assembly, to ionize the air; 5.The apparatus of claim 1, wherein the heat sink fins assembly comprisingstraight fins, pin fins, and irregular shapes fins structure;
 6. Theapparatus of claim 1, wherein the actuators comprising conductive traceson one side of the dielectric layer, and ground layer on the other sideof the dielectric layer; and multiplayer structure which have openingsfor microwave to generate micro-plasma and ions;
 7. The apparatus ofclaim 1, wherein the actuators comprising openings on the conductivelayers, on the wave guide structures, and on the cavity structures;wherein the openings are locations for electromagnetic microwave toionize the air to induce the ion driven turbulent gas flow;
 8. Theapparatus of claim 1, wherein the actuators are operable to couple witha fan, a heat pipe, a heat source, and a heat sink fins assembly togenerate the micro-plasma and ions;
 9. The apparatus of claim 1, whereinthe actuators may be made in a micron scale, a nano meter scale, and abulk scale;
 10. The apparatus of claim 1, the actuators may be coupledto a heat sink fins structure, and the actuators may be directlymanufactured on a silicon chip structure; and the actuators may bemanufactured with micro-electro-mechanical wafer processing techniques;11. The apparatus of claim 1, wherein the heat source may be amicroprocessor, an ASIC chip, a video processor chip, a graphicprocessor chip, an electronic IC chip, and a power supplier.